Although there might be something more straight forward, you might want to explore MIME::Entity. It is probably the best (but most detailed/involved way) to analyze/manipulate a message with attachments. The tricky part is determining whether or not you even have a message body text. As podmaster points out, you can use Mail::MboxParser, which is useful/easy for getting the body text or determining if there is one (example). Handling attachments is another matter and is not well documented in Mail::MboxParser.
in reply to Forwarding emails from my Unix Mailbox
That is where MIME::Entity might prove more useful. There is an example in the documentation showing how to "Muck about with the body data:" under "Manipulation examples". This will probably take a good bit of experimentation though.